OKX DEX API Guide: Building a Solana Token Swap Interface

npm install

REACT_APP_API_KEY=your_api_key
REACT_APP_SECRET_KEY=your_secret_key
REACT_APP_API_PASSPHRASE=your_passphrase
REACT_APP_PROJECT_ID=your_project_id
REACT_APP_USER_ADDRESS=your_wallet_address
REACT_APP_PRIVATE_KEY=your_private_key

import { Connection } from "@solana/web3.js";
import base58 from "bs58";
import cryptoJS from "crypto-js";

// Constants for tokens and chain
export const NATIVE_SOL = "11111111111111111111111111111111";
export const WRAPPED_SOL = "So11111111111111111111111111111111111111112";
export const USDC_SOL = "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v";
export const SOLANA_CHAIN_ID = "501";

// Initialize Solana connection
export const connection = new Connection("https://mainnet.helius-rpc.com/?api-key=<API_KEY>", {
    confirmTransactionInitialTimeout: 5000,
    wsEndpoint: "wss://mainnet.helius-rpc.com/?api-key=<API_KEY>",
});

// Environment variables for API authentication
const apiKey = process.env.REACT_APP_API_KEY;
const secretKey = process.env.REACT_APP_SECRET_KEY;
const apiPassphrase = process.env.REACT_APP_API_PASSPHRASE;
const projectId = process.env.REACT_APP_PROJECT_ID;

// Base URL for API requests
const apiBaseUrl = "https://www.okx.com/api/v5/dex";

/**
 * Gets swap data and optimal route from the OKX DEX API
 * Note: Requires API credentials from OKX Developer Portal
 * 
 * @param {Object} params 
 * @param {string} params.chainId - "501" for Solana
 * @param {string} params.amount - Amount in lamports (1 SOL = 1e9 lamports)
 * @param {string} params.fromTokenAddress - Source token (e.g., NATIVE_SOL)
 * @param {string} params.toTokenAddress - Destination token (e.g., USDC_SOL)
 * @param {string} params.slippage - Slippage tolerance ("0.5" for 0.5%)
 * @param {string} params.userWalletAddress - Solana wallet address
 * @returns {Promise<Object>} Contains routerResult.toTokenAmount and transaction data
 */
export async function getSingleChainSwap(params) {
    if (!apiKey || !secretKey || !apiPassphrase || !projectId) {
        throw new Error("Missing API credentials");
    }

    const timestamp = new Date().toISOString();
    const requestPath = "/api/v5/dex/aggregator/swap";
    const queryString = "?" + new URLSearchParams(params).toString();
    const headers = getHeaders(timestamp, "GET", requestPath, queryString);

    console.log("Requesting swap quote with params:", params);

    const response = await fetch(
        `https://www.okx.com${requestPath}${queryString}`,
        { method: "GET", headers }
    );

    const data = await response.json();
    if (data.code !== "0") {
        throw new Error(`API Error: ${data.msg}`);
    }

    if (!data.data?.[0]?.routerResult?.toTokenAmount) {
        throw new Error("Invalid or missing output amount");
    }

    return data.data[0];
}

/**
 * Executes a Solana transaction with retry logic and compute budget
 * @param {Object} txData - Transaction data from the API
 * @returns {Promise<Object>} Transaction result with explorer URL
 */
export async function executeTransaction(txData) {
    if (!userPrivateKey) {
        throw new Error("Private key not found");
    }

    try {
        // Get recent blockhash for transaction validity
        const recentBlockHash = await connection.getLatestBlockhash();
        const decodedTransaction = base58.decode(txData.data);

        // Create transaction object
        const tx = solanaWeb3.Transaction.from(decodedTransaction);
        tx.recentBlockhash = recentBlockHash.blockhash;

        // Create and add keypair for signing
        const feePayer = solanaWeb3.Keypair.fromSecretKey(
            base58.decode(userPrivateKey)
        );
        tx.partialSign(feePayer);

        // Send transaction with retry options
        const txId = await connection.sendRawTransaction(tx.serialize(), {
            skipPreflight: false,
            maxRetries: 5
        });

        // Wait for confirmation
        const confirmation = await connection.confirmTransaction({
            signature: txId,
            blockhash: recentBlockHash.blockhash,
            lastValidBlockHeight: recentBlockHash.lastValidBlockHeight
        }, 'confirmed');

        return {
            success: true,
            transactionId: txId,
            explorerUrl: `https://solscan.io/tx/${txId}`,
            confirmation
        };
    } catch (error) {
        console.error("Transaction failed:", error);
        throw error;
    }
}